1. Field of the Invention
The invention relates to a battery and a method of manufacturing the battery.
2. Description of the Related Art
Recently, as a power source for various portable devices, a group-battery comprising a plurality of alkaline storage batteries or the like connected together is generally used. In this type of group-battery, each of alkaline storage batteries, that is, a single cell has its outer surface covered in an outer package of a non-expensive material such as paper or a resin film to prevent a short circuit between each other.
For example, for a group-battery for a device such as a cellular phone, which does not has a very large load, an outer package made from a resin film is used. However, a large-current group-battery used as a power source for a power tool, a power-assisted bicycle and the like has a large load, and hence, the large-current group-battery often generates heat while used. Since the thermal resistance of a resin film is limited, an outer package of paper is generally used for a large current, as shown in Japanese Patent No. 3218820 Publication.
A battery covered in an outer paper package has an advantage that if an alkaline electrolyte leaks while the battery is used, the outer paper package absorbs the electrolyte and prevents it from leaking to the outside thereof.
In the large-current group-battery, rise in temperature during the use of it should be avoided. Hence, the large-current group-battery is generally cooled with a cooling blower provided in a case containing the group-battery.
However, when cooling air is brought in by the blower, water outside such as moisture is brought into the case at the same time and reaches the single cells. In that case, since the outer paper package which covers each single cell does not have water-repellency, the water penetrates the outer paper package and reaches the battery can inside. This causes a problem such that the battery can corrodes.
An object of the invention is to solve the above problem and provide a battery in which the corrosion of a battery can due to water outside can be prevented when the battery is used in a group-battery.